tri metal vs. bi metal bearings

[eejay56]

BPNW lists bi metal and tri metal heavy duty bearing sets. Are the heavy duty bearings worth the extra (twice as much) cost? Will they last significantly longer given a mildly built 1500 engine that sees spirited daily driving and occasional autocross use or is the money better spent elsewhere?

 

[poolboy]

There's a pretty good explanation or call it "sales pitch" on the Vandervell tri layered bearings in the TRF Blue Catalog on page 13.
I'd also be interested in the opinions of others on the Forum.

 

[Brosky]

I went with the Tri-Metal. The difference in cost now is nothing compared with a problem that could occur later. JMHO.

That bearing has been recognized as the "gold standard" for years for these cars.

Possibly more related to cost, but I'm not taking a chance at this point in the game.

 

[Andrew Mace]

Back in the days of the 948cc Herald engine, bi-metal bearings were installed on the 40hp single-carb engine, and tri-metal bearings were installed on the 50hp dual-SU-carb version of the same engine. From my admittedly non-engineering standpoint, 'nuff said!

 

[Moseso]

I bought the tri-metal bearings from British Parts Northwest (check their price) it was really only a few dollars more. Nothing close to "twice as much."

 

[foxtrapper]

Bearings are not a place to scrimp. Buy the best bearings you can get.

 

[tomshobby]

The tri-metal heavy duty bearing sets from BPNW are (or at least were) King bearings. King bearings are considered by many to be the best available.

 

[DNK]

Check my math but shouldn't they be only 50% more?
your only getting 1/2 again as much metal

 

[eejay56]

I bought the tri-metal bearings from British Parts Northwest (check their price) it was really only a few dollars more. Nothing close to "twice as much."

At BPNW bi-metal mains for a 1500 are 20.75 and the tri-metals are 44.22, crank bearings are 20.75 and 46.81 respectively. It sounds like the consensus is that it's money well spent.

 

[TR6oldtimer]

IMO, on a stock engine, the bi-metal babbitt bearings are fine. If you are running a racing or hopped up engine the tri-metal is preferred. The difference is the babbitt on the tri-metal is thinner making it less susceptible to fatigue breakdown, or so these diesel guys say.

https://www.marinediesels.info/2_stroke_engine_parts/Other_info/bearing_materials.htm

 

[poolboy]

Don't you guys think that he should get at least 50k miles with the standard bearings? A lot more with regular oil changes?

 

[TR6oldtimer]

Don't you guys think that he should get at least 50k miles with the standard bearings? A lot more with regular oil changes?

Easily and much more with proper oil and filter changes, the cylinders and valve assemble will wear out before the rod and mains. At least that has been my experience on a six.

 

[blkcorvair]

I bought the tri-metal bearings from British Parts Northwest (check their price) it was really only a few dollars more. Nothing close to "twice as much."

At BPNW bi-metal mains for a 1500 are 20.75 and the tri-metals are 44.22, crank bearings are 20.75 and 46.81 respectively. It sounds like the consensus is that it's money well spent.

With a polished 1500 crank and standrad bi metal bearings I was spinning 6k rpm + with no problems for more than 5000 Miles. (Before I found the PO installed the thrust washers backwards) NOT Advised. Any who the standard bearings held up execptionally well under that hard abuse and will many mods done. However I just bought Tri's to go with the crank Im currently having repaired..... My outlook though.. For daily driving if everything else is setupoo the right way it wont make a difference. But than again it is only $40 more :wink:

 

[StagByTriumph]

Hey guys, the top layer is really sacrificial and very thin. That is softest, in fact you can almost dent it with your fingernail, and is there for initial startup protection. The remaining two layers are the bulk of the thickness and strength.

 

[TR3driver]

That's true, but it doesn't keep it from being important. What it does is allow the bearing to "bed in" to the crank so the load is spread more evenly with less concentration of force to break down the harder layers underneath.

 

[vettedog72]

I think there is a lot of MOJO and MISTIQUE with the insert bearings being bi or tri-metal. I suspect a tri metal could be of less quality than some bi metals. But, because of my ignorance of the differences I just get the tri-metal because they are available and they are OEM in the "performance" motors. Also, the machine shop guy said the bearings I got from BPNW looked "pretty good"; that is a big complement from my machine shop.